...JavaConfig servlet and IoC configuration based on annotations wasn't much of an improvement comparing to the XML-based config.

...a functional way to configure http routes, security config or even beans, introduced in Spring 5, comes to the rescue!

... you'll find a showcase of how to configure your Spring Boot app (along with integration tests!!!) in a fully functional, declarative way, with a little help of a new shiny built-in Kotlin DSL helpers. A Kotlin's coroutines support in Spring is also leveraged here end-to-end (replaces the use of reactor).

...you'll find even more functional but experimental Spring configuration with spring-fu.

...you'll find the same Spring app, but configured with good old JavaConfig.

This server exposes:

• 2 RESTful http endpoints for creating and crediting a bank account
• a html resource Hello world webpage

These are fully covered by end-to-end integration tests, written in Spock framework.